Enforcement:

probable cause or plausible reasons to ask for warrant.
In the US, but could obviously interest the UK, a practice about mobile phone data, easily transferable to cybercrime given that the mobile phone technology is now computerised to the extreme some would say http://www.techdirt.com/articles/20071126/101924.shtml (26 November 2007)
the last comment on the article could be related to the notion of private/public divide that is being eroded with the internet, and needs a rethink http://www.techdirt.com/articles/20071203/095531.shtml (3rd December 2007)

investigators as preventive hackers
see the SOCA work about Microsoft OS to reveal its frailty...http://news.zdnet.co.uk/security/0,1000000189,39290736,00.htm (13 November 2007)

And an interesting question: "Can A Computer Store Tech Look At Your Files?" without warrant, (17th December 2007) http://www.techdirt.com/articles/20071214/182720.shtml